Security element and method for production thereof

ABSTRACT

The invention relates to an object, in particular a security element for security papers, bank notes, identity card or the like, as well as a security paper and a document of value with such a security element. Furthermore, the invention relates to a method for producing the object, in particular the security element or the security paper and the document of value with such a security element. The method in particular serves for manufacturing a precious-metal-coloured, preferably gold-coloured coating on a substrate.

This application is a National Phase of International Application SerialNo. PCT/EP03/03147, filed Mar. 26, 2003.

FIELD OF THE INVENTION

The invention relates to an object, in particular a security element forsecurity papers, bank notes, identity card or the like, as well as asecurity paper and a document of value with such a security element.Furthermore, the invention relates to a method for producing the object,in particular the security element or the security paper and thedocument of value with such a security element. The method in particularserves for manufacturing a precious-metal-coloured, preferablygold-coloured coating on a substrate.

BACKGROUND OF THE INVENTION

When producing documents of value, which within the framework of thepresent invention means bank notes, check forms, shares, identificationdocuments, credit cards, flight tickets and other deeds and documents aswell as labels, seals, packaging and other elements for protectingproducts, it is particularly important to make arrangements againsttampering and/or to take measures that permit the detection of theauthenticity. Apart from the features which can be detected or used whentesting is made by machines, there also exist features, which can beapplied to such documents by everybody without technical auxiliary meansand without any particular specialist knowledge for an unambiguousdetection of the authenticity.

One possibility to equip a security element, such as a security thread,with visually easily recognizable elements is described in EP 0 330 733B1, in which a security thread is provided with gaps in an opaque layer,and which contains colouring and/or luminescent substances in the gaps.This security thread is embedded in security papers as a so called“window security thread”, i.e. it is woven in the paper during the sheetformation of the security paper, so that in regular distances it isfreely accessible at the surface of the paper and fully embedded only inthe intermediate areas.

So as to increase the optical strikingness of a security element and toemphasize the value of the object to be protected, the security elementsoften are equipped with silver or gold colour tones.

One possibility to obtain a gold-coloured coating is to vapor-depositthin gold layers onto well reflecting grounds, such as e.g. aluminum orsilver. But due to the high costs of the source material and the greattechnical efforts required to manufacture very regular layers,profitability is not given.

Alternatively, also gold bronzes have been applied by means of vapordeposition with evaporation boat or sputtering. When vapor-depositingwith evaporation boat a wire is continuously fed into a hot boat. Whenthe boat is hot enough the just fed piece of wire immediately evaporizesand completely transitions into the vapor phase. A substrate locatedthereabove is coated with just that composition of this piece of wire.Within the boats, however, little lakes are often formed out of themolten wire, which e.g. consists of a certain alloy. From these lakesthe individual components of the alloy evaporate at different rates dueto different vapor pressures, the proportion of ingredients thereforebeing changed in the deposited material and thus on the substrate. Theinitially set colour tone thus continuously changes across the coatinglength and width of the item to be vapor-deposited during the vapordeposition process.

Furthermore, also the sputtering technique is used. Here metal clustersare knocked off from a fixed target in the plasma, which condense on thesubstrate disposed thereabove. The composition of the coating can bekept relatively constantly, but sputtering is a very time intensivetechnique and thus of very low productivity.

SUMMARY OF THE INVENTION

The invention is therefore based on the problem of providing a methodfor producing precious-metal coloured coatings, as well as objectscoated by means of such a method, in particular security elements anddocuments of value with such security elements. The method shall producea constant colour tone of the coating, in particular in a profitablemanner. The coated objects shall have, compared to prior art, anincreased forgery-proofness, e.g. due to their optically strikingappearance.

According to the invention by means of an electron beam or aresistance-heated crucible, while generating a multicomponent vapor,evaporating material is evaporated, which produces aprecious-metal-coloured multicomponent coating on a substrate.Electron-beam vapor deposition or vapor deposition by means ofresistance-heated crucible are vacuum coating methods, with the help ofwhich very thin, regular coatings can be applied. With electron-beamvapor deposition evaporating material located in a crucible is heated bymeans of an electron beam. With that vapor is generated, whichcondensates on the substrate guided thereabove. Instead of via theelectron beam the evaporating material can also be supplied with energyvia resistance heating of the crucible. The evaporating material can beliquid, as e.g. a molten metal, and is located in a crucible. Alsosubliming materials can be evaporated. The evaporation can take placeout of a crucible, the evaporating material in this case being e.g. amulticomponent system such as an alloy. Or the evaporating material canconsist of single components, which are located in separate crucibles.Each crucible is heated by one or several electron beams or byresistance heating. The crucibles are disposed in such a way, that thevapor lobes overlap each other above the crucibles. The heating power ofthe individual crucibles here is adjusted in such a way that amulticomponent coating, e.g. an alloy of the desired composition, isdeposited on the substrate.

BRIEF DESCRIPTION OF THE DRAWINGS

The following figures are schematic diagrams and do not necessarilycorrespond to the dimensions and proportions present in reality.

FIG. 1 shows an inventive document of value,

FIG. 2 shows a cross section of the inventive document of value alongthe line A-A and

FIG. 3 a, 3 b show a schematic structure of a vapor depositionapparatus.

FIG. 1 shows an inventive document of value in a top view. The shownexample is a bank note 1. This bank note has a strip-shaped securityelement 2, which extends across the whole width of the bank note 1. Thewhole surface of the security element 2 facing the viewer appearsgold-coloured.

The security element shown in FIG. 1 is a diffractive security element,which consists of an embossed plastic layer and at least onegold-coloured layer 3 produced according to example 1.

FIG. 2 shows a cross section along the line A-A in FIG. 1. Here theplastic layer 4 can be seen, where the diffraction structure is placedin. Thereabove and directly adjoining the inventive gold-colouredcoating 3 is disposed, into which a gap 6 is worked. The gaps can be anycharacters, alphanumeric characters, patterns, logos or the like.

The security element shown in FIG. 2 can be for example a securitythread. The security thread preferably consists of a transparent carrierfilm 4, on which the gold-coloured coating 3 is disposed.

FIG. 3 a schematically shows an experimental set-up, where in crucible 7is contained a Cu/Al-alloy 8. By means of an electron beam 9 the alloyis caused to melt and while supplied with further energy to evaporate.Above the crucible a vapor lobe 10 is formed having a certainCu/Al-composition. In this vapor lobe 10 is placed a film 12 guided on achill roll 11, and on the film 12 a Cu/Al-alloy of the desiredcomposition is deposited.

FIG. 3 b shows a process management alternative to that shown in FIG. 3a. The evaporating material here is composed of two single componentslocated in separate crucibles, namely Cu 13 in crucible 14 and Al 15 incrucible 16. The single components are molten and evaporated by means ofelectron beam 9, so that above the crucibles two vapor lobes 17, 18 areformed, which overlap each other in area 19. Due to this overlapping thevapor phase has a certain Cu/Al-composition. As described in FIG. 3 a afilm 12 guided on a chill roll 11 is placed in the vapor phase, so thatan alloy of Cu and Al in the desired composition can be deposited.

DETAILED DESCRIPTION OF THE INVENTION

Since the components of the evaporating material in general aresubstances with different evaporation rates, which depend e.g. on theprocess temperature and the vapor pressures of the individualcomponents, great demands have to be made on the method. So as to coat asubstrate with a certain composition, the vapor phase has to contain theindividual components in the desired quantity ratio. But it has to betaken into account that the quantity ratios, e.g. within a molten alloy,usually deviate from the quantity ratios within the vapor phase, whichis due to the different vapor pressures of the components, and thus haveto be appropriately adjusted. In the molten mass the proportion ofcomponents with a high vapor pressure usually has to be lower, whereasthe concentration of components with a lower vapor pressure usually haveto be present to a higher degree, so as to obtain the desired quantityratio in the vapor phase. The composition of the molten mass is chosenin such a way, that at a certain temperature the desired composition,which is to be deposited on the substrate, is present in the vapor.Furthermore, the composition of the evaporating material willcontinuously change during the vapor deposition process due to thedifferent evaporating rates of the individual components. This effectcan be compensated either by feeding certain components of theevaporating material or by using large volumes of molten mass.Preferably, the volumes of molten mass are chosen in such large amountsthat one coating cycle can be carried out without feeding any furtherevaporating material.

The vapor deposition of an alloy with a certain composition and adefined layer thickness preferably is controlled via a regulationmechanism, with the help of which the vapor-deposited layer is measuredin transmitted light and/or reflected light, possibly at several pointsacross the path width of the vapor-deposited substrate. For measuringthe transmission and/or reflection optical devices known to personsskilled in the art are used.

With transmission measuring the optical density of the deposited layeris measured and thus indirectly the thickness of the layer. If thevapor-deposited layer thickness varies from the preset value, it can beinfluenced by changing the path speed with which the substrate to bevapor-deposited is moved, and/or by the evaporation rate of thesubstance to be vapor-deposited. The evaporation rate here can becontrolled via the energy of the electron beam or the heating power. Ifthe layer thickness for example is higher than desired, the amount ofvapor-deposited substance per area unit can be decreased by increasingthe path speed. Alternatively or additionally, the evaporation rate canalso be reduced e.g. by lowering the heating power or by lowering theenergy of the electron beam.

With reflection measuring the colour of the deposited layer isspectrally measured and with that the composition of a multicomponentevaporating material is indirectly determined. Usually for that purposewhite light is irradiated, the reflected light spectrally analysed anddescribed with the help of colour coordinates, e.g. according to theMunsell system or the CIE system. The colour coordinates of thevapor-deposited layer are compared to a desired value definedbeforehand, which corresponds to a certain composition of theevaporating material, so that from a possible deviation a deviation inthe composition can be concluded and, if so, countermeasures can betaken. The regulation here is effected via changing the evaporation rateof the individual components in the multicomponent evaporating material,e.g. by increasing or decreasing the electron beam energy or the heatingpower.

When carrying out the regulation mechanism the following variations arethinkable. In the following preferred embodiments are described, wheretwo crucibles each contain one alloy component, the invention, however,not being restricted to these variations.

Variation A:

The heating power in crucible 1, which preferably contains the maincomponent of the alloy, is firmly set. The heating power is measured insuch a way, that the result is, as experience has shown, a metaldeposition of regular thickness across the whole width of the film thatusually amounts to one to two meters. The amount of the alloy maincomponent contained in crucible 1 here is dimensioned in such a way,that changes in the total heating power (sum of heating power incrucible 1 and crucible 2) has no effect on the layer thickness of thedeposited evaporating material. Measuring the transmission fordetermining the layer thickness is therefore not necessary. But whilethe film is coated, the colour coordinates of the vapor-deposited layerare measured in reflected light, possibly at several points across thepath width, and compared to a desired value defined beforehand. Thedeviations of one or several coordinates are then used to regulate theheating power in crucible 2. If crucible 2 is of a trough-shaped design,beside the heating power in crucible 2 possibly also the lateraldistribution of the heating power above the length of the trough can beregulated.

Variation B:

As in variation A the heating power in crucible 1, which preferablycontains the main component of the alloy, is firmly set, so that, asexperience has shown, a metal deposition of regular thickness across thewidth of the film is obtained. While the film is coated, the opticaldensity of the vapor-deposited layer is measured in transmitted light,possibly at several points across the path width. If values have beendetermined at different points of the path width, the average value ofthe optical density is calculated and compared to a given desired valuefor the layer thickness. In case of deviations the path speed, withwhich the film to be coated is moved, is regulated accordingly. Forregulating the heating power in crucible 2 the same method as inVariation A is used.

Variation C:

Here the evaporation rate in crucible 1 as well as in crucible 2 isregulated at a constant path speed, with which the substrate to bevapor-deposited is moved forward. The evaporation rates here again arecontrolled via the heating power or the energy of the electron beam. Theregulation of the evaporation rates here is influenced via thetransmission measuring of the optical density of the deposited layer aswell as by means of reflection measuring for determining the colourcoordinates. So as to produce a constant layer thickness and thus aconstant total amount of deposited material, the total heating power incrucible 1 and 2 preferably is of a constant value. For producing aconstant alloy composition the relation of the heating power in crucible1 to that in crucible 2 is preferably adjusted in a constant manner.

The evaporating material preferably is a multicomponent system, such ascompounds, mixtures or alloys, which produces a precious-metal colouredtone after being deposited onto the substrate. Within the terms of theinvention, “precious-metal coloured” means every colour tone whichcontains silver- and/or gold-coloured portions. Consequently, dependingon the composition of the evaporating material, the colour scale of thecoating does not only contain the pure silver or gold tones. The colorscale of silver tones ranges from a silver tone enriched with a whitecontent to silver tones with light to dark grey or even black content.The colour scale of gold tones ranges from light gold, nickel, gold todark gold and bronze. Additionally, by taking the respective measuresalso e.g. precious-metal coloured tones with tinges of yellow, green,red and brown can be produced.

Preferably, “precious-metal coloured” means gold-coloured, andgold-coloured here comprises any thinkable gold tone.

Preferably the evaporating material is an alloy, in particular goldbronze, “Gold bronze” within the terms of the invention means all thecopper base alloys, in particular alloys which comprise copper andaluminum. Further preferred alloys are alloys comprising copper and tin,alloys comprising copper and silver or alloys comprising copper, tin andsilver. Preferably the alloys deposited on the substrate comprise 95 to75 weight per cent, particularly preferred 95 to 85 weight per cent, andin particular preferred 92 weight per cent copper. In an embodimentparticularly preferred the alloy comprises 5 to 15 weight per centaluminum and 95 to 85 weight per cent copper. The layer vapor-depositedonto the substrate preferably is composed of 8 weight per cent aluminumand 92 weight per cent copper, so that the result is a gold-colouredtone.

For producing further colour tones, such as e.g. precious-metal tones,in particular gold tones, with tinges of yellow, green, red and brown,there exists the possibility of adding portions of foreign metal to thealloys. Suitable foreign metals are e.g. iron, manganese, vanadium,chromium, nickel, cobalt, silicon, magnesium, zinc or titanium.Preferably the portions of foreign metals amount to 5 weight per centreferred to the evaporating material deposited onto the substrate. Ofcourse there also exists the possibility of producing colour tones of amore silvery appearance e.g. by increasing the aluminum portion. Therespective composition of the evaporating material for producing thedesired colour tones on the substrate can be ascertained by a personskilled in the art by respective preliminary experiments.

The layer thickness of the vapor-deposited layer on the substratepreferably amounts to at least 20 nm up to a maximum of 200 nm, inparticular layer thicknesses of 50 up to 150 nm are preferred. Of courselayer thicknesses of less than 20 nm, for example layers of a thicknessof a few μm can also be used.

The multicomponent coating produced according to the invention can bedistinguished from those coatings that are produced by methods accordingto prior art, such as e.g. sputtering or vapor deposition withevaporation boat, by different crystalline structure parameters, such asparticle size, refractive index and conductivity. The analysis here canbe more or less elaborate depending on the parameter taken into account,but lies within the range of knowledge of a person skilled in the art.

The possibility of producing several gold-coloured tones also providesthe option to equip a security element with several colour tones. Theinventive security element, however, has at least oneprecious-metal-coloured coating. The optical impression rendered by sucha security element can be imitated, if at all, only with great efforts,in particular if different-coloured coatings are applied in complicatedpatterns. The security element can be a security thread which consistsof a self-supporting plastic film to which the precious-metal colouredcoatings are applied. This security thread can at least partially beplaced in a security paper or security document. But it is alsothinkable to form the security element in a ribbon-shaped orlabel-shaped fashion and to fasten it to the surface of the securitypaper or document of value.

Alternatively, the security element can also have the form of a transferelement. This variation is particularly advantageous, if the securityelement is disposed completely on the surface of the security paper ordocument of value. In this case the layer structure of the securityelement is prepared on a carrier film, usually a plastic film, and thentransferred in the desired outline contours to the security paper ordocument of value by means of a hot stamping method.

If the security element is disposed on the surface of the security paperor the document of value, it can have any outline structure, such as forexample round, oval, star-shaped, rectangular, trapezoidal orstrip-shaped outline contours. But the use of the inventive securityelement is not restricted to the sector of security documents. Theinventive security element can also be advantageously used in the sectorof product protection for protecting any goods from forgery. For thatpurpose the security element can have antitheft elements as well, suchas for example a coil or a chip. The same applies to the security paperor document of value that is provided with such a security element.

The substrate to be vapor-deposited preferably is a plastic film,preferably made of PET (polyethylene terephthalate), POP (polyphenyleneoxide), PEN (polyethylene naphthalate) or PC (polycarbonate).

Additionally, the plastic film of the security element can be providedwith diffraction structures in the form of a relief structure. Thediffraction structures can be any diffractive structures such asholograms or grating structures (e.g. Kinegram®, pixelgram) or the like.Usually these diffraction structures are embossed in the plastic film.

As a further optically striking feature also gaps can be worked into theinventive coating, preferably with the help of a washing method asdescribed in WO 99/13157 to which explicit reference is made herein.Here the security elements are prepared as a security film, which hasseveral advantages of the security element. The basic material is aself-supporting, preferably transparent plastic film. This plastic filmin the case of security threads or labels corresponds to the inventiveplastic layer of the security element. If the security elements aredissolved out from an embossed film, the plastic film forms the carriermaterial of this transfer material, to which the plastic layer isapplied in the form of a lacquer layer. In this lacquer layer or, incase of security threads or labels, in this plastic film diffractionstructures can be embossed. The inventive plastic layer of the securityelement is printed in the form of the future gaps, preferably by gravureprinting. For this a printing ink with a high pigment content is used,which forms a pored and raised applied ink layer. Then the coating isvapor-deposited to the printed plastic layer. As a last stage finallythe applied ink layer and the inventive coating on top of it are removedby washing out with a liquid, possibly combined with mechanical action.Preferably a water-soluble printing ink is used, so that water can beused as a liquid. With that this method is very environmentally friendlyand does not require any particular protective measures.

The washing out can be supported by mechanical means, such as a rotatingroll, brush or ultrasound.

The use of etching techniques is in a considerable manner moreelaborate, but in principle also possible. Here at first the inventivecoating is deposited onto the plastic layer and then the whole surface,except for the areas to be removed, is printed with a protective lacquerlayer. The whole security element layer structure is then guided throughan etching bath, in which the areas not covered are dissolved from theplastic layer. If for different coatings different etching bathes arenecessary, the covering process or the process of dipping into theetching bath has to be repeated with diverse etching solutions. Betweenthe different etching bathes neutralization and cleaning bathes have tobe provided, so that the chemicals of the different bathes are notrendered impure.

Other methods are also thinkable, such as e.g. mechanical removal of theinventive coating or producing the breaches by means of laser scriber,electron beam erosion or other removal processes.

The substrates vapor-deposited according to the invention can be furtherprocessed by e.g. mechanically scraping the vapor-deposited layer fromthe substrate, so that fine small plates are produced. These smallplates preferably can be worked into printing ink and as such be usedfor security elements.

The inventive coating method has the advantage that therewith in anextremely economic way, i.e. cost and time saving,precious-metal-coloured coatings can be produced, which compared toprior art are of an extremely regular design in view of colour tone andlayer thickness.

Due to their optically striking coating the security elements anddocuments of value produced according to the invention have aforgery-proofness increased accordingly, since they are recognizablewithout any further auxiliary means.

Further embodiments and advantages of the inventive method, securityelement or security paper and document of value are explained withreference to the example and the figures.

Example 1

In a electron-beam vapor deposition plant films made of PET,alternatively made of POP, PC or PEN, of a width of 1000 mm are coatedwith a layer thickness of approximately 55 nm made of 8 weight per centaluminum and 92 weight per cent copper. The evaporation is effected outof a crucible, the volumetric capacity of which is of at least such alarge amount that one coating cycle can be carried out without feedingfurther material. The evaporating material, an aluminum/copper alloy, isheated with an electron gun. Since copper has a higher vapor pressurethan aluminum in the molten mass, in the vapor the copper proportion ishigher than compared to the molten mass. On a substrate moved throughthe vapor thus a copper-coloured film would be deposited. As to avoidthis problem, the proportion of aluminum is increased relatively to thatof copper in the molten mass. For that reason 80% copper and 20%aluminum are used in the molten mass, which has a silvery colour tone.But the vapor above the molten mass has a copper aluminum proportion,which leads to gold-coloured deposits on a substrate having theabove-mentioned aluminum/copper proportion (8/92). During longer vapordeposition periods the mixture ratio changes in favour of aluminum dueto the higher evaporating rate of copper. This effect can be compensatedeither by feeding further copper or by using large volumes of moltenmass. When using large amounts of molten mass the mixture ratio during acoating cycle changes only slightly and the colour tone of thevapor-deposited layer remains regular.

Example 2

This embodiment corresponds to that described in example 1 and differsfrom example 1 in that the evaporating material is caused to melt andevaporate not by means of an electron beam, but by means of aresistance-heated crucible.

1. Method for producing a security element or transfer element for securing documents of value or for protecting products, comprising: vapor depositing a substrate with a multicomponent evaporating material, which is transformed into the vapor phase by means of electron beam or resistance heating, such that the evaporized evaporating material deposits as a precious-metal-coloured coating on the substrate; measuring a color composition of the coating by reflection measurement; comparing the measured color composition to a desired color composition; and correcting deviations in the color composition of the coating, from the desired color composition, by adjusting at least one of a heating power and an energy of an electron beam.
 2. Method according to claim 1, wherein the precious-metal-coloured coating is gold-coloured.
 3. Method according to claim 1, wherein the evaporating material consists of individual components in separate crucibles.
 4. Method according to claim 1, wherein the evaporating material is an alloy.
 5. Method according to claim 1, wherein the evaporating material comprises one or several metals from the group containing copper (Cu), aluminum (Al), tin (Sn) and silver (Ag).
 6. Method according to claim 1, wherein the evaporating material comprises Al/Cu or Sn/Cu or Ag/Cu or Ag/Sn/Cu.
 7. Method according to claim 1, wherein the coating comprises 5 to 15 weight percent aluminum and 85 to 95 weight percent copper.
 8. Method according to claim 1, wherein the evaporating material comprises at least one foreign metal.
 9. Method according to claim 8, wherein the foreign metal is chosen from the group of iron, manganese, vanadium, chromium, cobalt, silicon, magnesium, zinc or titanium.
 10. Method according to claim 1, wherein on the substrate are deposited different precious-metal-coloured coatings.
 11. Method according to claim 1, wherein the substrate is a plastic film.
 12. Method according to claim 1, wherein the coating is deposited in a layer thickness of 50 to 100 nm.
 13. Method according to claim 1, wherein before the coating process diffraction structures are embossed into the substrate.
 14. Method according to claim 1, wherein after the coating process the substrate is cut in a strip-shaped or ribbon-shaped fashion.
 15. Method according to claim 1, wherein the coating is removed from the substrate and broken into small plates, which, optionally, can be processed into printing ink.
 16. Security element or transfer element for securing documents of value or for protecting products, produced according to claim
 1. 17. Security element or transfer element according to claim 16, wherein the coating deposited on the substrate is at least one coating made of a precious-metal-coloured alloy.
 18. Security element or transfer element according to claim 17, wherein the alloy is gold-coloured.
 19. Security element or transfer element according to claim 17, wherein the alloy comprises copper.
 20. Security element or transfer element according to claim 17, wherein the alloy comprises at least one of aluminum, tin and silver.
 21. Security element or transfer element according to claim 17, wherein the alloy comprises 8 weight percent aluminum and 92 weight percent copper.
 22. Security element or transfer element according to claim 17, wherein the alloy comprises at least one foreign metal.
 23. Security element or transfer element according to claim 22, wherein the foreign metal is chosen from the group of iron, manganese, vanadium, chromium, cobalt, silicon, magnesium, zinc or titanium.
 24. Security element or transfer element according to claim 17, wherein the substrate is a plastic film.
 25. Security element or transfer element according to claim 17, wherein the coating has a layer thickness of 50 to 100 nm.
 26. Security element or transfer element according to claim 17, wherein the coating is at least partially overlaid with diffraction structures.
 27. Security element or transfer element according to claim 26, wherein the diffraction structures are embossed in the substrate.
 28. Security element according to claim 1, wherein the security element is a self-supporting label.
 29. Security element according to claim 1, wherein the security element is a security thread.
 30. Security paper for producing documents of value or document of value, characterized in that it has at least one security element according to claim
 1. 31. Security paper or document of value according to claim 30, wherein the security element is a security thread and embedded at least partially in the security paper.
 32. Security paper or document of value according to claim 30, wherein the security element is a transfer element, which is applied to the surface of the security paper.
 33. A method for protecting goods from forgery comprising incorporating therewith a security element or transfer element according to claim
 16. 34. A method for protecting goods from forgery comprising incorporating therewith a security paper or document of value according to claim
 30. 35. Printing ink produced according to claim
 15. 36. Method according to claim 1, further comprising determining a coating layer thickness by transmission measurement and correcting deviations in the coating layer thickness from a desired value by adjusting at least one of a heating power, an energy of an electron beam and a substrate path speed. 